A series of recent discoveries has scientists revising their image of Mars: They are now beginning to suspect that the Red Planet's geology may be more complex and Earth-like than previously imagined. New data suggests that the planet may have small bits of water spread around its surface. And it now seems that the planet's interior could once have been more geologically mature than previously thought.

The new data is courtesy of NASA's Curiosity, a car-sized robotic rover that has been exploring parts of the surface of Mars. Launched in 2011, the highly sophisticated vehicle is armed with an impressive arsenal of scientific instruments. In 2012, it landed in Mars' Gale Crater.

What has scientists excited is that Curiosity has detected traces of water. This water is chemically bound to the Martian dust that seems to be covering the entire planet. The finding is among several in the five studies published Thursday by the journal Science. It may explain mysterious water signals picked up by satellites in orbit around Mars.

The soil that covers Mars' surface in Gale Crater seems to consist of two major types, according to data from the rover's laser-shooting Chemistry and Camera (ChemCam) instrument. One is a coarse soil with millimeter-wide grains that probably came from the rocks around them. The other is very fine, with grains often a few micrometers in size.

Hydrogen Detected In Dust

The fine-grained soil doesn't really match the rocks around it, said Pierre-Yves Meslin, who led one of the studies. But it does seem to match the stuff found at sites where other rovers and landers touched down. That means it's probably distributed over much or all of the planet. Most likely it is kicked up and carried far in the fierce dust storms that can shroud the planet in a reddish haze.

The researchers say they don't know where that soil comes from. It may either be created in many places, or have one source that gets picked up and blown all over.

Either way, it's a handy, naturally averaged sample of the Martian surface.

Perhaps the most intriguing thing about this fine soil is that ChemCam's readings detected a hydrogen signal. Water, of course, is two-thirds hydrogen. This could explain why satellites orbiting Mars have picked up a mysterious water signal in the past, Meslin said.

"It's actually kind of exciting because it's water yet again on Mars, but it's in a different material than we had recognized," said geologist John Grotzinger, the mission's project scientist. "So what Curiosity is doing is just demonstrating that water is present in a number of ways. It just adds to the diversity."

CheMin And SAM Instruments

However, a study based on data from another of Curiosity's instruments came up with different results. The rover's Chemistry and Mineralogy (CheMin) tool - part of the dirt-digesting lab in its belly - found no sign of water in soil samples taken from a sandy dune dubbed Rocknest. That's because CheMin uses X-ray diffraction to bounce high-energy light off of a mineral's crystalline structure. If the soil isn't in crystalline form, there's no way for CheMin to see it.

All this means the hydrogen signal seen by ChemCam must have been coming from the non-crystalline portion of the soil, said David Bish, who led the CheMin study. This so-called amorphous portion makes up a significant part of the soil.

Sure enough, when Curiosity's Sample Analysis at Mars (SAM) instrument cooked up a tiny sample of soil in its little oven, it turned out that roughly 1.5 to 3 percent was made of water. The scientists think this water may have come from the atmosphere - that is, it might have been pulled out of Mars' thin air.

But while traces of water were found in the soil, Curiosity found no signs of minerals that had been formed in water. This was interesting, said Bish, as "one of the reasons for going to Gale Crater" was the assumption that it might be a good place to find clays containing such minerals. Inside Gale Crater lies a 3-mile-high mountain called Mt. Sharp, whose layers could be rich in clays. These might hold answers to whether Mars was once hospitable to life.

It's possible that the fine-grained soil on the surface of Mars is simply too young to have ever encountered liquid water, he said. If so, it would mean that many years passed between the formation of the water-rich clays locked inside of certain rocks and the dusty grains that currently cover the Martian surface.

"A More Evolved Planet"

Another of the studies focused on the rock known as Jake M, named after NASA engineer Jake Matijevic, who died shortly after the rover landed in 2012. Jake M is unlike any volcanic rock seen on Mars: It's rich in alkaline magma. This told the researchers that it had been created under high pressure - and perhaps in the presence of water, said Edward Stolper, lead author of the study.

In fact, it looks something like an uncommon rock on Earth called a mugearite. This is found on ocean islands and near underwater volcanos.

The rock's composition also told scientists that it was clearly made of the leftovers after other minerals in the Martian magma had crystallized out - that is, hardened into crystalline forms. That led them to believe that the heating and cooling and movement of magma that used to occur beneath Mars' mantle were a lot more complicated than they had thought.

"We see evidence for a more evolved planet," Grotzinger said, "so it looks like it was headed in more of a direction like Earth."]]> diversity mantle amorphous impressive intriguing significant composition magma coarse orbit atmosphere distributed